Military aircraft including helicopters and other vehicles and equipment subject to enemy fire commonly have self-sealing fuel tanks. Often these fuel tanks need to be supported after the impact of a ballistic or incendiary round while the fuel tank seals itself. Additionally, fire suppression systems are commonly used to suppress fires in the areas surrounding the fuel tanks. These systems suppress fires feeding on fuel leakage after impact of a ballistic round, during and after the tank self-sealing. In helicopters, the self-sealing fuel tank is often a fuel cell including a flexible outer wall and an inner wall of self-sealing soft material. The self-sealing fuel cell itself is supported within the vehicle by frames and backer boards spanning the frames. In other aircraft, self-sealing tanks are often integral to either the fuselage or aircraft wing.
Current ballistic protection systems for fuel tanks in military aircraft typically use foam or aluminum oxide fire suppression materials to prevent fires or explosion from incendiary rounds. Ballistic nylon backer boards made from plays of nylon impregnated with plastic are sometimes incorporated in fire protection systems to continue to support self-sealing fuel cells after a ballistic impact to assist the self-sealing function of fuel cells.
Fire protection systems used in fuel tank areas include active systems that spray or disperse fire suppression materials. The cost of installation and maintenance of such active systems is typically high. Other fire protection systems are passive systems. Passive honeycomb or sandwich structural panels incorporating fuel suppression powders can form a self-sealing fuel tank wall, or support a fuel cell during self-sealing, but load-bearing honeycomb or sandwich panels do not always rupture sufficiently upon a ballistic impact to disperse adequate fire suppressing powder. Custom-shaped non-load-bearing powder-filled sandwich panels or foam blocks incorporating fire suppression materials have been found to suppress fires from ballistic rounds. However, these panels or blocks must be specially shaped or cut and require additional supports, thereby complicating their installation.
Therefore, an unmet need exists for lightweight and easily installed systems to disperse fire suppression materials subject to ballistic fire, including areas surrounding fuel tanks in aircraft.